diff --git a/src/math/polysat/conflict_core.cpp b/src/math/polysat/conflict_core.cpp
index a48c8d138..eb919d336 100644
--- a/src/math/polysat/conflict_core.cpp
+++ b/src/math/polysat/conflict_core.cpp
@@ -240,19 +240,9 @@ namespace polysat {
             return false;
 
         if (conflict_var() == v) {
-            clause_builder lemma(s());
             forbidden_intervals fi;
-            if (fi.perform(s(), v, cjust_v, lemma)) {
-                // TODO: pass core to FI instead of a clause_builder?
-                reset();
-                for (auto lit : lemma) {
-                    auto c = cm().lookup(lit);
-                    insert(~c);
-                }
-                set_bailout();
+            if (fi.perform(s(), v, cjust_v, *this))
                 return true;
-            }
-            // TODO: add a dummy value for v?
         }
 
         m_vars.remove(v);
diff --git a/src/math/polysat/forbidden_intervals.cpp b/src/math/polysat/forbidden_intervals.cpp
index 44bbed09a..d9062bfb7 100644
--- a/src/math/polysat/forbidden_intervals.cpp
+++ b/src/math/polysat/forbidden_intervals.cpp
@@ -18,7 +18,6 @@ move "forbidden interval method from constraints
 
 --*/
 #include "math/polysat/forbidden_intervals.h"
-#include "math/polysat/clause_builder.h"
 #include "math/polysat/interval.h"
 #include "math/polysat/log.h"
 
@@ -73,14 +72,16 @@ namespace polysat {
     * We assume that neg_cond is a consequence of src that  
     * does not mention the variable v to be eliminated.
     */
-    void forbidden_intervals::full_interval_conflict(signed_constraint src, signed_constraint neg_cond, clause_builder& lemma) {
+    void forbidden_intervals::full_interval_conflict(signed_constraint src, signed_constraint neg_cond, conflict_core& core) {
         SASSERT(neg_cond);
-        lemma.push_new(neg_cond);
-        lemma.push(~src);
+        core.reset();
+        core.insert(~neg_cond);
+        core.insert(src);
+        core.set_bailout();
     }
 
-    bool forbidden_intervals::perform(solver& s, pvar v, vector<signed_constraint> const& just, clause_builder& lemma) {
-
+    bool forbidden_intervals::perform(solver& s, pvar v, vector<signed_constraint> const& just, conflict_core& core) {
+        
         // Extract forbidden intervals from conflicting constraints
         vector<fi_record> records;
         rational longest_len;
@@ -97,7 +98,7 @@ namespace polysat {
                 if (interval.is_full()) {
                     // We have a single interval covering the whole domain
                     // => the side conditions of that interval are enough to produce a conflict
-                    full_interval_conflict(c, neg_cond, lemma);
+                    full_interval_conflict(c, neg_cond, core);
                     return true;
                 }
                 else {
@@ -131,9 +132,6 @@ namespace polysat {
         LOG("seq: " << seq);
         SASSERT(seq.size() >= 2);  // otherwise has_full should have been true
 
-        // TODO lemma level depends on clauses used to derive it, not on levels of constraints
-        unsigned lemma_lvl = 0;
-
         // Update the conflict state
         // Idea:
         // - If the src constraints hold, and
@@ -142,6 +140,7 @@ namespace polysat {
         // then the forbidden intervals cover the whole domain and we have a conflict.
         // 
 
+        core.reset();
         // Add side conditions and interval constraints
         for (unsigned seq_i = seq.size(); seq_i-- > 0; ) {
             unsigned const i = seq[seq_i];
@@ -158,15 +157,16 @@ namespace polysat {
             // the level of a literal is when it was assigned. Lemmas could have unassigned literals.
             signed_constraint c = s.m_constraints.ult(lhs, rhs);
             LOG("constraint: " << c);
-            lemma.push_new(~c);
+            core.insert(c);
             // Side conditions
             // TODO: check whether the condition is subsumed by c?  maybe at the end do a "lemma reduction" step, to try and reduce branching?
             signed_constraint& neg_cond = records[i].neg_cond;
             if (neg_cond)
-                lemma.push_new(std::move(neg_cond));
-
-            lemma.push(~records[i].src);
+                core.insert(~neg_cond);
+            
+            core.insert(records[i].src);
         }
+        core.set_bailout();
         return true;
     }
 
diff --git a/src/math/polysat/forbidden_intervals.h b/src/math/polysat/forbidden_intervals.h
index 8182d1266..fd927fb9f 100644
--- a/src/math/polysat/forbidden_intervals.h
+++ b/src/math/polysat/forbidden_intervals.h
@@ -20,9 +20,9 @@ Author:
 namespace polysat {
 
     class forbidden_intervals {
-        void full_interval_conflict(signed_constraint c, signed_constraint neg_cond, clause_builder& lemma);
+        void full_interval_conflict(signed_constraint c, signed_constraint neg_cond, conflict_core& core);
         bool get_interval(solver& s, signed_constraint const& c, pvar v, eval_interval& out_interval, signed_constraint& out_neg_cond);
     public:
-        bool perform(solver& s, pvar v, vector<signed_constraint> const& just, clause_builder& lemma);
+        bool perform(solver& s, pvar v, vector<signed_constraint> const& just, conflict_core& core);
     };
 }
diff --git a/src/math/polysat/solver.cpp b/src/math/polysat/solver.cpp
index 7d0b556ff..2278eeb9f 100644
--- a/src/math/polysat/solver.cpp
+++ b/src/math/polysat/solver.cpp
@@ -467,7 +467,7 @@ namespace polysat {
             if (item.is_assignment()) {
                 // Resolve over variable assignment
                 pvar v = item.var();
-                if (!m_conflict.is_pmarked(v))
+                if (!m_conflict.is_pmarked(v) && !m_conflict.is_bailout())
                     continue;
                 justification& j = m_justification[v];
                 LOG("Justification: " << j);